1. Field of the Invention
The present invention relates to seed dryers. More particularly though not exclusively, the present invention relates to an apparatus and method for controlling the temperature and air flow direction of a seed dryer.
2. Problems in the Art
In the agricultural industry seed is frequently harvested at moisture levels exceeding that which would permit safe and a long term storage. The crops are harvested while the moisture content is high in order to help prevent reductions in quality of the seeds from things such as insects, disease, or exposure to adverse weather. This high moisture harvesting of seed is only possible when combined with artificial drying to bring the seeds down to an acceptable moisture level. The drying process must occur under strictly controlled conditions in order to maximize the quality of a seed product. Factors such as the rate and the temperature at which seed dries has a large effect upon the seeds' germination and storability.
Typical prior art seed dryers are usually comprised of single pass dryers with air supplied from a common plenum or two-pass reversible dryers. In a single pass dryer, all of the bins will receive air having the same temperature. With a two-pass dryer, the bins can receive air having only one of two possible temperatures and one flow rate. Typically, hot air from the upper plenum is forced, in a first pass, through the corn from top to bottom, feeding the lower plenum with lower temperature and higher relative humidity air, then in the second pass, air is forced through another bin from bottom to top, then exhausted to the outside. High moisture corn is first dried with second pass air, then as moisture lowers, it is dried with first pass air. Changing bins from second pass air to first pass air is called reversal. Two-pass dryers require careful management to insure that roughly equal numbers of bins receive first and second pass air in order to maintain a balanced static pressure in the plenums. Also, reversal of the air flow through the bins can occur only once during the drying process. In either single pass or two-pass dryers, the precise control of the drying process is not possible. FIG. 1 shows a typical prior art two-pass dryer (described below).
Other prior art drying systems regulate the air temperature of individual bins by supplying drying air from individual burners (or heating coils) and fans for each bin. This prior art system permits individual bin temperature regulation, but with typical large drying installations having a plurality of bins, the cost of acquiring and maintaining all of the necessary individual burners and fans is prohibitive.
The concept of mixing high and low temperature streams of air is used in the heating and cooling of buildings. It is also known to control the temperature of water from a faucet by mixing various proportions of hot and cold water.
3. Features of the Invention
A general feature of the present invention is the provision of a method and apparatus for drying seed which overcomes problems found in the prior art.
A further feature of the present invention is the provision of a method and apparatus for drying seed which permits the complete control of the drying process on an individual bin basis.
A further feature of the present invention is the provision of a method and apparatus for drying seed which uses an electronic controller to control the precise temperature and direction of air flow through the seed to be dried.
A further feature, objects and advantages of the present invention includes:
An apparatus and method for drying seed which uses a mixing plenum to selectively mix certain amounts of relatively hot and cold air to provide air having a desired temperature for drying the seed.
An apparatus and method for drying seed which uses an upper and lower door to blow air either above or below the seed to be dried and adjustable exhaust ports located above and below the seed to be dried in order to selectively control the direction of air flow through the seed.
An apparatus and method for drying seed which controls the airflow direction through the seed to maintain consistency within a bin.
An apparatus and method for drying seed which uses an electronic controller to control the operation of various doors to precisely mix the hot and cold air as well as control the air flow direction through the seed.
An apparatus and method for drying seed which uses a programmable logic controller to control the operation of the dryer.
An apparatus and method for drying seed which includes temperature sensors to sense the temperature of the air blown into the bin.
An apparatus and method for drying seed which measures the static pressure above and below the seed in the bin to control the air flow through the bin.
An apparatus and method for drying seed which optimizes dryer capacity, energy efficiency, and seed quality.
An apparatus and method for drying seed which uses a plurality of drying bins which is capable of precisely controlling the temperature of air entering each bin without the need for individual fans and burners for each individual bin.
An apparatus and method for drying seed which uses fuzzy logic to control the temperature and flow of air through the bin.
These as well as other objects, features and advantages of the present invention will become apparent from the following specification and claims.